Police said they have offered their deepest sympathy to the family during this difficult time.

SafeKids Aotearoa director Ann Weaver said the incident was a tragedy.

"I do sympathise with the family for their loss and as well the driver," she said.

SafeKids Aotearoa has campaigned for drivers to be vigilant when reversing out of driveways if children are present. It was important to walk around your car before getting in to drive and the same message applied in carparks, she said.

"It's really important if you are in any situation, before you get in the car you walk around to see if there are any children," she said.

"People don't realise what they can't see when they are in a car.

"If you're reversing, you wouldn't see a 2-year-old behind you for up to 10m."

Cowles Stadium in Christchurch's Aranui is a purpose-built, standalone indoor stadium.The stadium is run by the Christchurch City Council with basketball, netball, volleyball and badminton courts for hire. It has an on-site carpark.